The larynx is responsible for protecting the lower airway, permitting ventilation, and for the production of voice. These critical laryngeal functions are altered by aging, and may be caused by mechanisms related to sarcopenia (i.e., the loss of skeletal muscle mass, organization, and strength). However, the underlying biological mechanisms that may cause laryngeal sarcopenia are unclear. Senescent individuals exhibit a pattern of structural and functional adaptations within the vascular system that may contribute to sarcopenia, such as a reduction in skeletal muscle blood flow, and decreased capillary density. In our laboratory, we have found age-related changes in microcirculatory geometry in a rat larynx in vivo model. However, our work within the laryngeal microvascular system has been hampered by cumbersome, and perhaps inaccurate, measurement techniques. In the proposed exploratory/developmental research project, we plan to develop innovative methods for studying blood flow in the larynx of living animals, using microscale Particle Image Velocimetry (5PIV). Our hypothesis is that alterations in blood flow have a causal influence on sarcopenia of laryngeal muscles. We plan to test this hypothesis in a future R01 application using muscle physiology, microvascular physiology, biochemistry, and molecular biology methods. In order to perform this future work, however, exploratory/developmental research first must be performed to develop innovative methods for studying blood flow in the larynx of living animals. The proposed research has 3 specific aims. Aims 1 and 2 are milestone-driven, while Aim 3 is hypothesis-driven. Our aims are: (1) To develop and implement the 5PIV technique to measure blood flow in muscles, (2) To manipulate red blood cell velocity and acceleration to determine if 5PIV measures are sensitive to treatment-related changes, and (3) To determine whether aging effects capillary laryngeal muscle blood flow via 5PIV quantification and to determine the implications for oxygen exchange. This work is innovative and important because the mechanisms whereby aging impacts laryngeal muscle function are largely unexplored. Our exploratory study will allow the development of a cutting-edge technique to investigate such mechanisms in future studies, including the effects of therapeutic interventions, such as electrical nerve/muscle stimulation and exercise. Accordingly, this work will lay the groundwork for future studies aimed at understanding mechanisms underlying cranial muscle sarcopenia. PUBLIC HEALTH RELEVANCE: Alterations in blood flow to muscles in the larynx may have a causal influence on the age- related muscular decline that underlies functional decrements in voice and swallowing. This work will use state of the art imaging techniques (micro Particle Image Velocimetry) to develop a method of measuring the velocity of red blood cells (RBCs) in a laryngeal muscle and to test the hypothesis that microvascular hemodynamics are altered in aging muscles. This exploratory/developmental research project will develop new methodology to allow accurate, mechanistic, and hypothesis-driven future research focused on an important clinical problem.